Prosecutors wield tremendous power, which is kept in check by a set of unique ethical obligations. In explaining why prosecutors sometimes fail to honor these multiple and arguably divergent obligations, scholars tend to fall into two schools of thought. The first school focuses upon institutional incentives that promote abuses of power. These scholars implicitly treat the prosecutor as a rational actor who decides whether to comply with a rule based on an assessment of the expected costs and benefits of doing so. The second school focuses upon bounded human rationality, drawing on the teachings of cognitive science to argue that prosecutors transgress not because of sinister motives, but because they labor under the same cognitive limitations that all humans do. In this article, I begin to unify these two schools of thought into a comprehensive approach. I apply the lessons of cognitive science to identify the ways in which prosecutors’ distinctive institutional environment may undermine not just their willingness to play fair, but their ability to do so. Research on the psychological effects of accountability demonstrates that when people are judged primarily for their ability to persuade others of their position, they are susceptible to defensive bolstering at the expense of objectivity. I argue that prosecutors operate under precisely such a system, and are therefore particularly susceptible to biases that undermine their ability to honor obligations that require some objectivity on their part. In support of this claim, I present the results of two original experiments demonstrating that holding people accountable for their ability to persuade others of a suspect’s guilt exacerbates common cognitive biases relevant to prosecutorial decision making, and discuss the implications of this research for reform.